Go构造函数类型 [英] Go constructor type

问题描述

  //客户端可用于向客户端发送请求Google地图WebService API 
类型客户端结构{
 httpClient * http.Client 
 apiKey字符串
 baseURL字符串
 clientID字符串
签名[]字节
 requestsPerSecond int 
 rateLimiter chan int 
} 
 
 // ClientOption是NewClient（...）的构造函数选项的类型。 
类型ClientOption func（* Client）错误
 
 var defaultRequestsPerSecond = 10 
 
 // NewClient构造一个新的客户端，它可以向Google Maps WebService API发出请求。 
 func NewClient（options ... ClientOption）（* Client，error）{
c：=& Client {requestsPerSecond：defaultRequestsPerSecond} 
 WithHTTPClient（&http.Client {}）（c ）
 for _，option：= range options {
 err：= option（c）
 if err！= nil {
 return nil，err 
} 
} 
 ..... 
  

我不明白发生了什么事ClientOption。它是一个指向客户端的函数类型，它返回一个错误？然后在NewClient中，它看起来像需要一个ClientOption类型的数组并返回一个指向Client的新指针。我不确定这是否正确，如果任何人都可以更多地解释，或者给我一个类似于很多Javascript库的类比

  options：{
 property1：someproperty，
 property2：another property
} 
  

在构造函数中。

解决方案

ClientOption是一个接受客户端指针并返回一个错误（可能为零）。

例如，下面是一个创建ClientOption函数的超时函数：

<$ p $客户端选项{
返回func（c *客户端）错误{
c.timeout =持续时间
返回零
}
}

NewClient函数接受可变数量的ClientOption参数，选项'切片。它创建一个新的客户端，通过将客户端指针传递给每个ClientOption来配置它，并返回指针。

它可以按如下方式使用：

  client：= NewClient（WithTimeout（3 * time.Second））
  

请参阅自我参考功能 Rob Pike和Dave Cheney的选项文章。

I was wondering if someone could explain this syntax to me:

// Client may be used to make requests to the Google Maps WebService APIs
type Client struct {
    httpClient        *http.Client
    apiKey            string
    baseURL           string
    clientID          string
    signature         []byte
    requestsPerSecond int
    rateLimiter       chan int
}

// ClientOption is the type of constructor options for NewClient(...).
type ClientOption func(*Client) error

var defaultRequestsPerSecond = 10

// NewClient constructs a new Client which can make requests to the Google Maps WebService APIs.
func NewClient(options ...ClientOption) (*Client, error) {
    c := &Client{requestsPerSecond: defaultRequestsPerSecond}
    WithHTTPClient(&http.Client{})(c)
    for _, option := range options {
        err := option(c)
        if err != nil {
            return nil, err
        }
    }
    .....

I don't understand what's going on with ClientOption. Is it a function type on pointer to client that returns an error? And then in NewClient, it looks like it takes in an array of ClientOption types and returns a new pointer to a Client. I'm not sure if that's right and if anyone can explain that more or give me an analogy similar to what a lot of Javascript libraries do with

options: {
    property1: "someproperty",
    property2: "anotherproperty"
}

in a constructor.

解决方案

A ClientOption is a function accepting a client pointer and returning an error (probably nil).

For example, here's a timeout function creating a ClientOption function:

func WithTimeout(duration time.Duration) ClientOption {
    return func(c *Client) error {
        c.timeout = duration
        return nil
    }
}

The NewClient function accepts a variable number of ClientOption parameters, available in the 'options' slice. It creates a new Client, configures it by passing client pointer to each ClientOption, and returns the pointer.

It could be used as follows:

client := NewClient(WithTimeout(3 * time.Second))

See self referential functions by Rob Pike, and Dave Cheney's options article.

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